With the higher recording density of a hard disk drive (HDD), a demand has been made that the mounted thin film magnetic head is further made narrow in track width and gap length and further enhanced in the sensitivity. At the present day, there has been used the thin film magnetic head having a write head and a read head combined together. A giant magnetoresistive (GMR) head using the GMR effect has been mainly used as the read head. The GMR head is a head of the CIP (current in plane) type which allows an electric signal to flow in the sensor film in parallel to the film plane. In order to further improve the recording density in the future, a TMR (tunneling magneto resistive effect) head and a CPP-GMR (current perpendicular to a plane-giant magneto resistive effect) head which appear to be advantageous to the high output have been actively developed in narrowing the tracks and the gaps. The TMR head and the CPP-GMR head are different from the conventional GMR head, and not the CIP type head that allows the electric signal to flow in the sensor film in parallel to the film plane, but the CPP type head that allows the electric current to flow therein in a direction perpendicular to the film plane, which is largely different therefrom.
Japanese Patent Publication No. 2002-26423 (“Patent Document 1”) discloses a method of etching the sensor film. In the method, etching operation is divided into two steps, and a first step is conducted at an etching beam incident angle (milling angle) of about 20°, and a second step is conducted at the incident angle of about 75°. The above etching process taking re-deposition removal into consideration is disclosed in a process of etching the write head. Japanese Patent Publication No. 2000-105906 (“Patent Document 2) has proposed that a step A and a step B are repetitively conducted several times, the etching operation is conducted in the step A, and the re-deposition removal is conducted in the step B. When it is assumed that the incident angle of the step A is θA, and the incident angle of the step B is θB, a relationship of θA<θB is satisfied.
Japanese Patent Publication No. 2003-198000 (“Patent Document 3) discloses a CPP-GMR head that is the CPP type head. A lower lead that comes in contact with the sensor film has a convex configuration, and a width that comes in contact with the sensor film of the upper lead is made smaller than the lower lead, to thereby improve an alignment margin and form a fine contact portion. Japanese Patent Publication No. 2004-241763 (“Patent Document 4”) has proposed that in order to prevent the characteristics of the TMR head from being deteriorated due to an annealing process, a film for protecting a wall surface of the sensor film is arranged after the sensor film has been etched.
Also, in order to further increase the output, the sensor per se has been increasingly improved. For example, in the case of the TMR, alumina: Al-Ox has been generally known as a barrier layer. When MgO is used as the barrier layer, another MR ratio is obtained. Also, in the case of the CPP-GMR, an oxidized layer is partially arranged on a part of the sensor film, to thereby improve the MR ratio.
In the CPP type head, the upper and lower shields that are used as the magnetic shield also serve as electrodes. Then, an insulator is disposed on a wall surface of the sensor film, and electrodes are disposed on the upper and lower surfaces of the sensor film to allow a current to flow in a direction perpendicular to the film surface. In the case of the above CPP type head structure, an influence of re-deposition that occurs when the sensor film is etched becomes very remarkable. For example, in the case of the TMR head, magnetic layers are disposed on the upper and lower surfaces of a tunneling barrier layer that generates the tunneling effect as the sensor film structure. However, when the re-deposition layer is formed on the etching wall surface of the tunneling barrier layer when the sensor film is etched, the re-deposition layer forms a leak path of the current with the result that the electric resistance and the electric output are significantly decreased.
In the case where the sense current is allowed to flow in the direction perpendicular to the film surface as described above, when an undesired current path, that is, short-circuiting occurs between the upper and lower leads, the current path causes a fatal defect. In particular, the re-deposition in the sensor film etching process as described above is liable to cause the short-circuiting. In order to prevent the short-circuiting that is attributable to the above re-deposition, the re-deposition removal is conducted. However, there is a fear that the sensor film is damaged in the re-deposition removing process. A manufacturing method including the re-deposition removal will be described with reference to FIG. 24. In this example, the TMR film is used as the sensor film. After a track forming resist mask (etching mask) 4 has been formed on the sensor film 3 as shown in FIG. 24(a), an Ar beam is input at an incident angle θA as shown in FIG. 24(b) to etch the TRM film. A re-deposition 33 is formed thicker as the incident angle θA is smaller. In the case where the etching operation has been completed in that state, short-circuiting occurs on the re-deposition 33, to thereby cause the fatal detect. Under the circumstances, as shown in FIG. 24(c), the Ar beam is input to the incident angle θB to remove the re-deposition 33. As usual, the incident angle θB to be used is about 65° to 75°. Because it is difficult to etch only the re-deposition in the re-deposition removing process, the sensor film 3 is slightly etched by the Ar beam. That is, because the sensor film wall surface per se is irradiated with the Ar beam, there is a fear that the magnetic layer and the barrier layer are damaged, and the interface of those multilayer films is damaged.
It appears that the influences of the above re-deposition and damage get further serious by narrowing the tracks in the future. The reason is that, for example, in the case of the re-deposition, the head resistance becomes larger as the tracks are made narrower, and an influence of the resistance reduction due to the re-deposition is increased as much as the head resistance is increased. In the case of the damage, the ratio of the damage to the width or volume of the sensor film becomes large, and the MR ratio appears to be smaller. Also, there is the possibility that the resistance of the damaged portion becomes low as with the re-deposition, and the characteristic deterioration occurs as with the above-mentioned re-deposition.
In Patent Document 1, the sensor film is etched in a first process, and the re-deposition that has been formed in the first process is removed in a second process. When it is assumed that the beam incident angle in the first process is θ1 (about 20°), and the beam incident angle in the second process is θ2 (about 75°), a relationship of θ1<θ2 is satisfied. In this case, there is a fear that the sensor film is damaged in removing the re-deposition. Also, there is a fear that the configuration of the sensor film end is deteriorated by the re-deposition removal. The sensor film is formed of a multilayer film made of diverse materials, and there is the possibility that the etching rates of the respective layers are different from each other. For that reason, there is the possibility that roughness occurs on the wall surface due to the difference in the etching rate to generate the configuration failure in the re-deposition removing processes.
Since it appears that the influences of the re-deposition and the damage become further serious by narrowing the tracks in the future as described above, there is considered that it is effective to widely form the sensor film as disclosed in Patent Document 3. This is because the adverse effect of the re-deposition and the damage is effectively reduced when the sensor film is widened. However, the side reading from the track side is liable to occur as the sensor film is wider, and it seems that an improvement in the recording density due to the narrowed tracks is difficult.
Japanese Patent Document 4 discloses the characteristic deterioration prevention of the TMR head in the write head annealing process, but fails to disclose the characteristic deterioration prevention in etching the TMR film.
In the above-mentioned conventional art, the characteristic deterioration of the CPP type head is prevented by the re-deposition removal etching process of the sensor film, the sensor film end protection, or an enlargement in the sensor film. However, there is no specific disclosure as to the etching configuration of the sensor film. Also, the characteristic stabilization due to the domain control film is important, but a relationship with the end configuration of the sensor film is uncertain. In the future, it is estimated that diverse novel sensor films are developed in order to further increase the output. However, there is the possibility that a damage on the sensor film becomes remarkable due to the etching operation or the re-deposition removal.
A tendency is made that a material of the barrier layer in the TMR head changes from the conventional alumina to MgO. This is because the output can be further increased with the use of MgO. Under the circumstances, an MgO-TMR head manufacturing using the etching method including the re-deposition removal has been studied. FIG. 25 is a diagram showing the characteristic of the head that has been obtained through the conventional manufacturing method. FIG. 25 shows that the obtained head characteristic is normalized by the film characteristic with the use of a resistance-area product (RA) and the MR ratio (MR) which are indexes indicative of the CPP type head characteristics. The obtained head characteristics are remarkably deteriorated in the RA and the MR due to the characteristic of the film per se. Separately, the configuration has been observed, but the clear re-deposition has not been found. From that fact, it is estimated that the characteristic deterioration is caused by the influence of the damage due to the re-deposition removing process. It is estimated that the damage is the metallization due to an oxide defect from the barrier layer or the mixing of the barrier layer and the magnetic layer together.